1. Field of the Invention
This invention relates to method and apparatus for NAS and CAS storage systems and, more specifically, unifying NAS/CAS storage systems.
2. Related Art
Transactional data, i.e., data that is regularly accessed and modified is generally stored on a network attached storage (NAS) system. NAS systems are well known in the art, so that no further discussion is necessary herein to describe NAS systems.
With the rapid increase in the amount of digital data, the amount of fixed or reference digital contents is also growing rapidly. Generally, fixed digital data refers to digital data that does not undergo changes or editing, such as email, x-ray, voice archive, and so on. Much of these fixed contents are required to be retained for a long term, safely, and at low cost. For example, fixed data may be required to be preserved for regulatory compliance, litigation, etc. Therefore, such data needs to be stored securely and at low cost, but readily available for future retrieval.
Recently, content addressed storage (CAS) systems have been developed for archiving fixed data. As noted above, archived data must be kept unchanged for a long term. There are two typical file access methods for CAS: one is using general network file system protocols, such as NFS or CIFS, while the other is using contents ID calculated by the file name or its contents. Content address is a unique identifier of archived data, derived from the data content itself. The CAS system calculates hash value of the archived data by using hash algorithm such as MD5, SHA1 or SHA 256. Other features of CAS include, for example, write prohibition, retention period management, customer metadata addition, data integrity check, etc. For more information about CAS system and addressing, the reader is directed to U.S. Pat. No. 7,096,342.
Conventionally, the NAS and CAS systems are separate and independent systems that are linked via a communication channel, e.g., a network. Consequently, users who need both NAS and CAS systems need to acquire and maintain two separate systems and link them via a communication channel to ensure proper archiving of data. A conceptual diagram of an example of a prior art NAS and CAS linked systems is shown in FIG. 1, illustrating, among others, existing method of archiving. When the NAS client 1000 stores files of transactional data, the files are stored in storage system 3200 of NAS system 3000. When files stored in storage system 3200 need to be archived, they are transferred to storage system 4200 of CAS system 4000 via network 5000. When the file is stored in storage system 4200 various features are associated with the file, such as, e.g., meta data, retention policy, write protect, etc.
In one example of prior art archiving, illustrated in FIG. 1, the CAS client 1200 mounts a file system whose export name is nas1 3500 as /nas1, and mounts a file system whose export name is cas1 4500 as /cas1. Based on the pre-determined policies, which were set by an administrator, the policy management program 1212 invokes the migration program 1214. The migration program reads a file from the NAS such as “/nas1/a.txt”. The migration program invokes a metadata management program 1213. The metadata management program adds some custom metadata for the file in order to help searching and retrieval of the file when necessary. The migration program writes the file and metadata on CAS such as “/cas1/a.txt”. The file retrieval from the CAS system is also executed by the archive application 1211.
The inventor of the subject application has appreciated that such prior art systems present several issues. First, the purchase and maintenance of two separate systems present a burden on organizations requiring both a NAS and CAS systems. Second, the necessity for transmitting files to be archived from the NAS to the CAS system over the network presents network bandwidth and security issues.